It started with a horrifying knife attack where the perpetrator stabbed 11 children and killing 3 of them. 2 adults were also stabbed. This attack horrified the nation.
News stories alleged that the perpetrator was an Islamic illegal immigrant, social media did what it does best: whipping up emotions and exaggeration and feeding it to people with poorer standard of education.
The background here is that there are concerns surrounding illegal immigration in the UK, as it is sold by criminal gangs as a country of neverending riches. Some opinions are justified, and some are not.
As you can imagine,far right organisation jumped on this as an excuse to encourage shitty behaviour, and the worst of them used it as an excuse to have a tantrum and damage peopkes properly, attack people of different ethnicities and get themselves locked up for it.
TL:DR : Horrible racist and bigoted individuals made a tragedy about them, and now we all have to deal with their shittiness.